It was noted that the irritation due to the lice caused scratching, and that thereby lice became crushed on to the skin. An emulsion was made of two infected lice and rubbed on to the slightly excoriated skin of one of the above workers. Infection followed five days later. A drop of emulsion placed on the conjunctiva of the human eye produced spirochætosis after an incubation of seven days. The body contents of such lice, then, produce infection when they reach the blood by any excoriated or penetrable surface. The stages leading up to infection in nature briefly are: The irritation due to the louse bites causes scratching, and the lice are crushed on to the skin. The slight abrasion is quite sufficient to permit the entry of the parasite. The louse bite alone is harmless. Infection by way of the eye is quite probable in Africa, remembering the constant trouble due to sand, dust, insects, etc., resulting in frequent touching of the eyes.
The spirochætes occur in the body fluid of the lice and can pass in it to the adjacent organs. Thus they probably find their way into the genital organs, and into the eggs of the lice. Eggs laid twenty to thirty days after the parent became infected have retained the infection, and the larvæ issuing from such eggs must have contained some form of spirochætes, for an emulsion of either the eggs or the larvæ produced spirochætosis when inoculated into monkeys. Further details regarding the spirochætosis in the eggs of the lice and in the larvæ are needed. Hereditary infection, however, has been demonstrated, but is not very common. Sergent and Foley (1914) state that the spirochæte possesses a very small and virulent form which it assumes during apyrexial periods in man and during a period following an infecting meal in the louse. Nicolle and Blanc (1914) find that the organisms are infective in the louse just before they reappear as spirochætes. Nicolle and Blaizot found that female lice were more susceptible to spirochætes than males, four times as many females as males being infected.
Tictin (1897) found S. recurrentis in bugs recently fed on patients, and infected a monkey with the fluids of crushed bugs. Karlinski (1902) found the spirochætes in bed-bugs in infected houses. There is some other evidence to show that bugs may transmit the spirochæte in Nature. Further researches are needed regarding the relationship of bed-bugs and human spirochætosis.
Multiplication of S. recurrentis is by longitudinal and transverse division (including so-called “incurvation”), and the organism forms small, ovoid bodies (“coccoid” bodies) in the same way as S. duttoni.
S. recurrentis is the cause of European relapsing fever, and a number of possible varieties of it are associated with relapsing fevers in other parts of the world. Such spirochætes only differ by biological reactions, such as acquired immunity tests. They include:—
S. rossii, the agent of East African relapsing fever; S. novyi, the agent of North American relapsing fever; S. carteri, the agent of Indian relapsing fever; S. berbera, the agent of North African and Egyptian relapsing fever.
Other Human Spirochætes are:—
S. schaudinni. This organism, according to Prowazek, is the agent of ulcus tropicum. It varies in length from 10 µ to 20 µ.
S. aboriginalis has been found in cases of granuloma inguinale in British New Guinea and Western Australia. It also occurs in dogs, and may not be truly parasitic.
S. vincenti. This spirochæte is 12 µ to 25 µ in length, tapers at both ends and has few coils. It has been associated with angina vincenti. It often occurs in company with fusiform bacilli.
S. bronchialis, found by Castellani in 1907 in cases of bronchitis in Ceylon. The parasites are delicate, but show morphological variation. This organism is important and has since been found in the West Indies, India, Philippine Islands and various parts of Africa, such as the Anglo-Egyptian Sudan, Uganda and West Africa. It has recently been the subject of research by Chalmers and O’Farrell, Taylor, and Fantham.
S. phagedenis was found by Noguchi in a ten days old ulcerated swelling of the labium. The organism shows much variation in size, being 4 µ to 30 µ in length.
S. refringens (Schaudinn, 1905) occurs in association with Treponema pallidum in syphilitic lesions, but is non-pathogenic. It is 20 µ to 35 µ long and 0·5 µ to 0·75 µ broad, being larger than T. pallidum and more easily stained.
Various spirochætes have also been notified in vomits, chiefly in Australia; others from the human intestinal tract, e.g., S. eurygyrata; S. stenogyrata (Werner); S. hachaizæ (Kowalski), in cholera motions; S. buccalis (Cohn, 1875) and S. dentium occurring in the human mouth and in carious teeth (S. dentium, Koch, 1877, being the smaller); S. acuminata and S. obtusa found by Castellani in open sores in cases of yaws.
Animal spirochætes of economic importance include:—
S. anserina, highly pathogenic to geese.
S. gallinarum (= S. marchouxi) in fowls. (See p. 119.)
S. theileri in cattle and S. ovina in sheep also occur in Africa; their pathogenicity is not clear.
S. laverani (= S. muris), occurring in the blood of and pathogenic to mice, is probably the smallest spirochæte from the blood, being only 3 µ to 6 µ long.
Numerous spirochætes have been recorded from the guts of various mammals, birds, fishes, amphibia and insects.
Cultivation of Spirochætes.—Cultures of spirochætes have been made with little success or with great difficulty until comparatively recently, when Noguchi (1912) devised a means whereby he has cultivated most of the pathogenic spirochætes as well as some Treponemata.
Noguchi has now cultivated S. duttoni, S. recurrentis, S. rossii, S. novyi and S. gallinarum from the blood; S. phagedenis157 from human phagedænic lesions; S. refringens158 and spirochætes from the teeth.
His method is as follows:—
A piece of fresh, sterile tissue, usually rabbit kidney, is placed in a sterile test-tube. A few drops of citrated blood from the heart of an infected animal, e.g., rat or mouse, is added, and about 15 c.c. of sterile ascitic or hydrocœle fluid is poured quickly into the tube. Some of the tubes are covered with a layer of sterile paraffin oil, others are left uncovered. The tubes are incubated at 37° C. The best results are obtained if the blood is taken from an animal forty-eight to seventy-two hours after it has been inoculated, that is, before the spirochætes reach their maximum multiplicative period in the blood. The presence of some oxygen seems indispensable for these blood spirochætes, and they fail to develop in vacuo or in an atmosphere of hydrogen.
For subcultures, 0·5 c.c. of a culture is added to the medium instead of citrated blood, and it is useful to add a little fresh, normal blood, either human or from an animal, such as a rat.
Noguchi found that the events in cultures were:—
S. duttoni,159 maximum multiplication on the eighth to ninth day; disintegration beginning on the tenth day, spirochætes disappeared after about the fifteenth day. No diminution of virulence was found at the ninth day.
S. rossii (= S. kochi).160 Maximum development on the ninth day, after which the virulence diminishes. The incubation period is also prolonged.
S. recurrentis161 (= S. obermeieri). Maximum growth on the seventh